A watch case formed of an equally substantial percentage of copper has already been proposed in the patent document CH-A-543 764. Herein the manufacturing process of elements making up a watch case is characterized by the fact that one employs a copper beryllium alloy adapted to structural hardening by heat treatment, one machines said elements, then deposits on the exterior thereof a non-oxydizing layer of metallic material. The document also indicates that the copper beryllium alloy includes at least 1.8% and at most 2.05% of beryllium and that the heat treatment permitting structural hardening thereof comprises annealing effected at 320.degree. C. over a period of at least two hours. Further, in accordance with this document, the method proposed also enables obtaining, by known and tested means such as stamping, turning, threading, piercing, milling as well as machining by means of diamond tools and by simple heat treatment, a strong watch case all the elements of which may receive a surface hardening treatment enabling the watch to maintain intact a pleasing and almost unchangeable appearance during an almost unlimited time period, even if it is worn under very severe conditions.
From the description which has just been given, it may be assumed that machining of a watch case employing the base material as described is not particularly simple in the sense that it requires several successive operations in order to arrive at the case in its final state. This is probably due to the employment of beryllium which renders the copper brittle and not very malleable which thus necessitates operation by stages prior to obtaining the finished product.
Beryllium alloyed with copper or bronze finds electrical applications where it has been frequently employed as spring electrical contacts. It however presents a serious difficulty which is that of being toxic. Beryllium and its salts must be handled with the greatest of care. It must not be touched in order to check the effect of softness which it exhibits. It is thus necessary to observe a certain work discipline when it is known that a concentration in the atmosphere exceeding two milligrams per cubic meter is dangerous. For these reasons at present beryllium and its alloys are difficult to stock as is likewise difficult the problem of handling and treating the waste.
The patent document SU 154 669 describes an electrically conducting alloy having a base of at least 95% copper, the remainder including cadmium among others. It is known that cadmium is toxic and must be avoided at all costs.
The employment of copper in the pure state presents however a great interest which is that of being readily deformable in the cold state and frequently to require only a single operation to arrive at the object sought for. Pure copper however presents insufficient mechanical strength for certain employments as here the obtaining of a watch case. It will be noted also that the cold forming of pure copper may bring about cracking thereof. It is thus necessary to improve the mechanical resistance by adding to the copper certain elements which enable increasing its rigidity and hardness and this whilst avoiding the employment of toxic elements such as beryllium and cadmium.